1. Technical Field
Illustrative embodiments generally relate to an optical unit including optical elements such as a lens and a photoelectric converter element configured to receive a light beam focused by the lens in which positions of the optical elements can be adjusted, an image reading device including the optical unit, and an image forming apparatus including the image reading device.
2. Description of the Related Art
In related-art image reading devices, for example, light is directed onto an original document (hereinafter “document”) and a photoelectric converter element comprised of a CCD, a CMOS, or the like receives the light reflected from the document and converts that light into electrical signals, so that the document is read as photoelectrically converted image data. The basic configuration of one example of such related-art image reading devices is shown in FIG. 1.
As illustrated in FIG. 1, such an image reading device has as a light source a xenon lamp 101 having a generally cylindrical shape extending in a main scanning direction. The xenon lamp 101 directs light onto a document placed on a contact glass 102, and the light reflected from the document is directed to a photoelectric converter element 104 via a lens 103. As described above, the photoelectric converter element 104 converts the light into electrical signals.
The above-described image reading device further includes a first carriage 106 including the xenon lamp 101 and a first mirror 105 configured to deflect the light reflected from the document, and a second carriage 109 including a second mirror 107 configured to further deflect the light deflected by the first mirror 105 and a third mirror 108. Each of the first carriage 106 and the second carriage 109 runs below the contact glass 102 at a predetermined scanning speed to read the document placed on the contact glass 102.
The lens 103 and the photoelectric converter element 104 are both mounted in an image reading unit 120, and therefore whenever the light striking a light-receiving surface of the photoelectric converter element 104 deviates from the optical axis of the lens 103 and the photoelectric converter element 104, an image of the document is not properly read. To ensure that the quality of the read image satisfies design standards, the relative positions of the document and the lens 103, and the lens 103 and the photoelectric converter element 104 are adjusted as appropriate, after which the lens 103, the photoelectric converter element 104, and a photoelectric converter element control circuit 121 are fixed in place in a support member 122.
Although there are many methods by which this adjustment can be carried out, the lens 103 and the photoelectric converter element 104 may, for example, be fixed in place with an ultraviolet adhesive after adjusting the relative positions thereof using a jig. However, such an arrangement increases the size of the jig and thus the cost of the device.
To solve such problems, one recent approach involves an image reading device having cutouts provided in a lens unit. Use of such cutouts enables optical adjustment of the lens unit to be carried out using a smaller jig such as a slotted screwdriver.
However, because lens conjugate distances vary greatly over a wide range, when the lens and the photoelectric converter element are moved together as a single unit along the optical axis to adjust magnification, a larger jig such as a movable stage is required to cope with such adjustment over a wide range.